Fukushima Update: A Very Bad Situation

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Well, it now turns out that many of my worst fears about Fukushima have been confirmed with the news that TEPCO has finally admitted that Reactor #1 has experienced a meltdown event that may have breached the primary containment vessel. Further, truly alarming levels of radiation are now being reported in and around Tokyo.

The prospects for containing the situation at Reactor #1 are now much dimmer than previously admitted. A melted core is far more difficult to cool because the geometry of the slag heap at the bottom is not nearly as favorable as long thin tubes around which water can be relatively easily circulated.

Worse, if the slag has either melted through the primary containment vessel or somehow leaked out through a fitting that has failed, then the ability to circulate water is even more compromised.

Uranium fuel in at least one of the six reactors at Fukushima has melted, the operator of the crippled nuclear plant has said. The admission effectively torpedoes a plan to flood the overheating fuel with water and bring a quick end to the worst nuclear crisis since Chernobyl.

Tokyo Electric Power Co (Tepco) said water levels have fallen at least one metre below fuel rodsinside Reactor 1 and that melted fuel has dropped to the bottom of the reactor's containment vessel. Engineers are working inside the reactor building for the first time since the crisis began when a hydrogen explosion blew off its roof following the huge quake and tsunami on 11 March.

Tepco general manager Junichi Matsumoto told reporters in Tokyo that the discovery means its timetable to entomb the containment reactor vessel in water may have to be scrapped. "We can't deny the possibility that a hole in the pressure vessel caused water to leak," Mr Matsumoto said.

Observers fear that Reactor 3, which contains MOX plutonium fuel, may have also suffered a meltdown, and the situation inside Reactor 2 is still shrouded in mystery.

The idea that fuel rods have melted (a process that begins at around 2,600 degrees F but requires 3,400 degrees F in order to melt the zircaloy cladding) coupled with the admission that the roughly 5-inch-thick steel containment vessel have been breached (presumably by being melted through) is completely, utterly, and inexcusably at odds with the temperature data TEPCO has released to date for the core.

At no time has TEPCO ever reported a temperature higher than ~750 degrees F (400C), and it has more typically reported primary containment temperatures barely one third that high.

With steel being an excellent conductor of heat, it is just simply not possible for melting to occur and for the reported temperatures to have been that low. Either something as basic as temperature monitoring is out of the realm of the possible for TEPCO's engineers (with troubling implications for where we really are in this unfolding disaster), or TEPCO has been falsifying the temperature data that it has been releasing.

This, too, has troubling implications, for it means that the rest of the data - including the radiation readings and isotopes discovered - are all suspect, too. Neither bodes well, so pick your poison.

I am now very suspicious of the water level data, as well, because TEPCO is now admitting (sort of) that that they can't deny the possibility that there's a hole in the primary containment vessel. Unless that hole is magically at the same level as the water readings, there's something wrong with their water level data. The process I am imagining is that the core melted down and somehow punctured or penetrated the bottom of the vessel. If true, then the water level in there is essentially zero, not "one meter below the fuel rods," as claimed.

Worrying Images From Helicopter 'Over Flight' Video

Last week we analyzed a few stills from the helicopter fly-over. This morning I came across this next video, which at first I thought was the same, but I quickly realized it had additional footage taken from the beginning of the fly-over that I had not yet seen. It also seems to have slightly different views than the prior one, so it may be a different video shot with a different camera taken during the same flight (the final images of Reactor #4's smoke line up). It has an enormously interesting but troubling feature in it that I only discovered by crawling through the video frame by frame (that's how desperate I am for any hard information about the reactors).

Here's what I found. Between seconds 30 and 31 in the video, as it scans across the rubble of Reactor #1 (presumably; orientation is not easy at this part of the video), we see a fissure that appears to be emanating a bright white-orange light. The link is here (better hurry, I bet this one gets pulled too), and I've arranged some stills from the video below. They are presented in series, meaning the top one is from second 30 of the video progressing to the bottom one from second 31.

In all, we have numerous frames taken from quite different angles, some in and some out of focus, indicating that what we are looking at is not a video anomaly caused by light reflecting off of some bent metal or other such artifact.

Okay folks, that looks very much like a hot spot. A very hot spot. If we knew what it was made out of, we could probably identify it to within a few degrees of its actual heat value, but we don't know what it is (besides a fissure that is glowing at an orange-white temperature).

But I am disinclined to believe it is a normal fire burning up normal materials, because there have been no reports or videos or photos showing smoke emanating from this reactor. Still, it remains one possibility.

Another less-desirable but not dismissible possibility is that it is coming from some sort of nuclear reaction, be it residual decay heat or even a meltdown-driven process. We just don't have enough information to tell, and the authorities have been less than forthcoming with this bit of information.

A seat-of-the-pants analysis, which borders on the irresponsible because we don't know anything about the camera, its settings, or what is emitting the light, allows us to speculate that the temperature of the hot spot is well over 1,000 degrees Celsius. If it were metal, say iron, glowing that color, our guess would be in the vicinity of 5,000 degrees Celsius.

Here are several views of the glowing spot against a black-body temperature chart (note that a Kelvin is the same thing as a Celsius but they start at different place…zero for Celsius is freezing water and for Kelvin it is absolute zero. To convert, just subtract -273 from the Kelvin scale and you've got Celsius).

Of course, we have no idea about what is glowing down there, so it is impossible to say anything for sure, besides, "That's a very hot spot."

It is not yet time to turn our attention off of this situation. Yes, it is good news that nothing else seems to have exploded or gone much worse in a few days, and for that I am grateful and hopeful. But the utter lack of information leaves me concerned that something is being hidden from our view.

No Chance of Hooking Up All The Pumps

One stated goal of the authorities is to hook up the pumps in Reactors #1, 3, and 4. A power line has been brought in, and this is supposed to provide hope.

Also in that helicopter fly-over was a nice stable view of Reactor #3 from the air. Please look at this and decide for yourself how likely it is that the pumps and wiring and plumbing are all in place to allow for the pumps to be turned on any time soon.

It was only yesterday that functions were fully checked out and restored in the control room - a building that didn't get turned to rubble. Therefore, we might question just how quickly the systems might be restored at the decimated reactor structures, especially if the repair crews are operating out of a Type 74 main battle tank.

My conclusion from this line of thinking is that while we should still hope for speedy restoration of systems, we should plan as if weeks and months might be involved.

As it turns out, we now have a reasonable understanding of what the 'crack of doom' probably was: the heat signature from a melting core. The title of the piece quoted above is "Japanese Reactor Situation Far Worse Than Admitted," and I guess we can now say that the admissions are finally catching up with what we already knew.

As always, trusting our own abilities to know what we are looking at and make reasonable guesses turns out to be the right course of action, especially during times when official sources have conflicts of interest in being truly open and honest.

I use the term "official sources" loosely because it is also true that it was not just TEPCO that had access to the heat signature data detected above. It must also be true that the US, which conducted numerous fly-overs with sophisticated detection packages, had this information as well.

We had clues about this when the NRC official made an at-the-time shocking statement that a partial meltdown had 'probably' occurred.

TOKYO, May 13 (Xinhua) -- A radioactive substance of up to 170,000 becquerels per kilogram was detected in incinerator ashes at a sewage plant in Koto Ward, east Tokyo, in late March, the Kyodo News Agency quoted government sources as saying Friday.

The highly-contaminated ashes were discovered following the nuclear crisis at the Fukushima No. 1 nuclear plant which escalated through March as a hydrogen explosion exacerbated the disaster and highly radioactive water was both discharged and found to be freely flowing into the Pacific Ocean.

The ashes have since been recycled into materials used for construction, such as cement, sources with knowledge of the matter said.

In addition, the sources revealed that also in late March a radioactive substance, which may or may not have been cesium, measuring 100,000-140,000 becquerels per kg, was found in two other separate sewage facilities in the Itabashi and Ota areas of Tokyo.

Separately on Friday, the local government of Maebashi, the capital city of Gunma Prefecture, said radioactive cesium of 41,000 becquerels per kg was detected in incinerator ashes collected Monday at a water sanitation facility.

This is outrageous and shocking news. First, because of the levels, and second, because these things were detected in "late March" and then hidden from the public to such an extent that the screaming hot ashes were allowed to be recycled into and used for construction materials. Now that's a cover-up.

A becquerel is one decay per second. So if you had a Geiger counter up against a radiation source that was emitting just two becquerels, you'd hear a reasonably steady tick-tick-tick-tick sound. By one hundred becquerels, you would be hard-pressed to hear the ticks as separate events - the sound would be a blurred staccato. By one thousand becquerels, it's just a squeal, and there's no point in listening anymore, as your ears are not helpful in trying to gauge the level of radiation.

Now look back at those radiation readings in the hundreds of thousands per kg. They are incredibly hot. An average brick is in the vicinity of a kilogram, so think of holding one in your hands while it emits 170,000 radioactive decays per second.

Okay, so this is a very, very hot reading.

And here's where those readings were detected:

These readings are all within a ten-mile radius of Tokyo.

Further south of Tokyo, in the Kanagawa prefecture seen to the lower left of the above image, tea was recalled:

TOKYO—A prefecture just south of Tokyo said it had detected higher-than-permissible amounts of radioactive material in tea leaves, in a reminder that Japan's radioactive-contamination problems are far from over.

The contamination—the first case in nearly a month that an agricultural product has been found tainted outside Fukushima Daiichi's home prefecture—is also the first time that any agricultural item from Kanagawa Prefecture, which includes Yokohama, was found to contain an excessive level of radioactivity.

According to Kanagawa officials, a sample of tea leaves collected May 9 from the city of Minamiashigara, in the western part of the prefecture, was found to contain 550 becquerels of cesium per kilogram in the first test; the second test of the same sample detected 570 becquerels. The difference between the two readings is within the margin of error in such tests, the officials said.

While it is a bit disturbing to have that much radiation be found that far from the Fukushima site, here we note that a Becquerel count in the 550 range is at least a number we can get out minds around. It is still far too high a reading - and I wish we knew the isotopes involved, as they are crucial to determining whether there isn't possibly a greater concern from the type of contamination vs. the radioactivity itself. By this I mean that if the contaminants involved are iodine or strontium, the greater concern is one of bioaccumulation and deposition, which can enormously magnify the health risks for a given level of radioactivity.

What the Japanese people, as well as the rest of the world, need very badly right now is one of the most comprehensive radiation and contamination mapping projects ever conducted.

If I lived over there, I would get myself a sensitive radiation/dosimeter and I would be personally scanning all of the food and water my family consumed, and my immediate surroundings as I lived, worked and played. If levels beyond what I considered safe were detected, I would then leave.

The 170,000 becquerel reading is just so far off the charts, and is so far beyond my personal safety limit, that there's a nearly 100% chance that if I were living in the Tokyo area my family and I would have left as soon as I heard the readings.

Similarly, frighteningly high levels of radiactive cesium were found in the soils around Tokyo, in amounts that are higher than those TEPCO or the Japanese government have released for most of the Fukushima prefecture itself:

Moving on to the latest developments in Japan's ongoing nuclear crisis highly radioactive substances were detected in parts of Tokyo.

Japan's Asahi Shimbun reports about 3,200 and nearly 2-thousand becquerels of radioactive cesium per kilogram were found in the soil of Tokyo districts of Koto and Chiyoda, respectively, from testing conducted between April 10th and the 20th.

This amount is higher than what was found in the prefectures near the Fukushima plant and experts warn that other areas may be subject to radiation contamination as clusters of clouds containing radioactive material remain in the atmosphere.

One could reasonably ask how such a finding is possible this many miles away from Fukushima, given the prevailing wind patterns and the (allegedly) lower findings far closer to the plant itself. At least these tests are only a month old...perhaps someday real-time results will become available to the people of Japan.

My faith in TEPCO and the Japanese government (which blocked Greenpeace from conducting its own radiaiton sampling in Japanese territorial waters) is very close to zero.

Fairewinds Associates Has The Best Coverage

The very best ongoing coverage of the Fukushima disaster is coming from Arnie Gundersen of Fairewinds Associates. He is experienced and very, very clear about when he knows, what he suspects, and what he doesn't know. I really appreciate that approach, as you almost certainly already know.

He recently postulated that the explosion seen in the Reactor #3 complex was initiated in the spent fuel pool and was much more than a simple hydrogen explosion (which is quite obvious, really, from the video of the explosion), and was an example of what he calls a 'prompt moderated criticality'.

Without going into all the details, it is a form of what we might call a nuclear, rather than a chemical, explosion.

Significant differences exist between this type of event and what we might call a true nuclear explosion. But all the same, it was a very exothermic, high-energy release that most likely drew its power from a briefly-sustained fast neutron reaction.

As Mr. Gundersen reported, pieces of the spent fuel pool rods were found up to 2 kilometers away, implying an initial ejection speed in the vicinity of 1,000 miles per hour. But we already knew that the Reactor #3 explosion was something far more energetic than a simple hydrogen explosion, and it's good to know that there's a reasonable explanation even if it is rather frightening to know that such a thing can happen in a spent fuel pool.

By the way, this would be another example of something that many of the nuclear apologists said could 'never happen' - and yet which happened. Other examples would be breach of the primary containment, breach of the secondary containment, and large-scale release of radiation into the environment.

Also it should be noted here that a private food firm in Japan tested its own rice fields 50 km from Fukushima and detected in plutonium on far higher concentrations than any TEPCO or government tests had yet revealed (link: need to translate to English.)

The Remaining Fears

The good news is that nothing has blown up lately at the Fukushima complex, indicating some sort of stability as well as the likelihood that the reactors, while a complete mess, are not going to do anything more dramatic than they've already done.

The bad news is that Reactors #1, #2, and #3 are all really badly damaged and leaking contamination to the outside world. Pouring water on them only creates more radioactive water that will find its way into the groundwater and/or the ocean.

The fear is that the molten cores are still cooking along, slowly working their way out of first the primary containment vessels and that they might slowly eat their way out of the secondary containment vessels, too. If this happens, there will be a very real chance of extremely large-scale release of radioactive contamination -possibly in a rather vigorous manner - should some sort of re-criticality be established or just a good-old-fashioned steam explosion occur if/when the molted cores encounter water.

Can we rule out another, possibly larger, 'prompt criticality' event? No, not at this stage.

Another fear centers on the fact that we've not yet been treated to full disclosure on the amount and types of radiation released. Is there still significant iodine-131 being released more than 60 days after the beginning of this event? If so, that will mean that criticality is still going on or has recently happened? Because by this stage, more than 99% of the initial 1-131 has decayed away.

The difference between fighting the leftover decay heat and trying to deal with re-critical fuel is like night and day. The former is slowly cooling off naturally; the latter is generating heat.

So, yes, we need and deserve to know exactly what the isotopes are that are being found, in what proportions, and whether there are pockets of criticality in any of the damaged reactors.

As Predicted...

Just based on the evidence we had and the amount of damage we could see, it was obvious early on that this event would drag on for months. Now it looks like 'years' is a better guess. Certainly it is already well past the point of relevance to most news organizations, and it is hard to get good information from major news organizations outside of Japan these days.

The primary worry right now is that the situation at Fukushima Daiichi is not yet stabilized. Every time I think they have turned the corner, more news is released that indicates that there are still surprises emerging from the site.

Water escapes, unexpected isotopes are detected (I-131 in the Reactor #4 fuel pool), and meltdowns and reactor breaches are finally admitted.

Given that this is still something of a two-steps-forwards/one-step-backwards situation, we should now consider what will happen if/when a typhoon comes and blows all the contamination inland in far greater quantities than have yet occurred.

Even without renewed criticality generating fresh isotopes, the amount of material that is highly dangerous is immense.

We can hope and pray that they manage to get things under far better control before too much longer, but so far the scale of the disaster has proven a formidable foe.

Conclusion

The Fukushima situation is still not what we might call stabilized, and it may not be for some months yet, especially if re-criticality has occurred.

The amounts of radiation detected all the way south of and in and around Tokyo is alarming, especially the sludge findings in the hundreds of thousands of becquerels.

Anybody living there should invest in radiation detection equipment and begin practicing basic decontamination procedures as a matter of routine if unsafe levels are detected. Obtaining food from sources as far south and west as possible is prudent practice.

The problem is not the levels of radiation; the danger lurks in the ingestion of contamination, especially of isotopes that tend to concentrate in the body. Strontium, iodine, and cesium all have that tendency.

I wish there were better news to report, but this is the situation as it stands: Fukushima is not over, not by a long shot.

Workers at Japan's Fukushima plant say the ground under the facility is cracking and radioactive steam is escaping through the fissures. They also say pipes and at least one reactor were seriously damaged before the tsunami hit the area in March.

The allegations raise concerns that the facility was doomed even before the earthquake triggered the disaster. Problems with deteriorating pipes at the plant had been reported for years. The cooling system failed to stop reactors going into meltdown after it was hit by the 40-metre-high waves. The plant has been leaking radioactive material ever since, despite efforts to clean it up.The allegations raise concerns that the facility was doomed even before the earthquake triggered the disaster. Problems with deteriorating pipes at the plant had been reported for years. The cooling system failed to stop reactors going into meltdown after it was hit by the 40-metre-high waves. The plant has been leaking radioactive material ever since, despite efforts to clean it up.

“We use a Lagrangian particles dispersal method to track where free floating material (fish larvae, algae, phytoplankton, zooplankton…) present in the sea water near the damaged Fukushima Daiichi nuclear power station plant could have gone since the earthquake on March 11th. THIS IS NOT A REPRESENTATION OF THE RADIOACTIVE PLUME CONCENTRATION. Since we do not know how much contaminated water and at what concentration was released into the ocean, it is impossible to estimate the extent and dilution of the plume. However, field monitoring by TEPCO and modelling by the Sirrocco group in University of Toulouse, France both show high concentration in the surrounding water (highest rate at 80 Bq/L and 24 Bq/L for respectively I-131 and C-137) . Assuming that a part of the passive biomass could have been contaminated in the area, we are trying to track where the radionuclides are spreading as it will eventually climb up the food chain.

The dispersal model is ASR’s Pol3DD. The model is forced by hydrodynamic data from the HYCOM/NCODA system which provides on a weekly basis, daily oceanic current in the world ocean. The resolution in this part of the Pacific Ocean is around 8km x 8km cells. We are treating only the sea surface currents. Particles in the model are continuously released near the Fukushima Daiichi power plant since March 11th. The dispersal model keeps a trace of their visits in the model cells. The results here are expressed in number of visit per surface area of material which has been in contact at least once with the highly concentrated radioactive water.”

The government's Nuclear and Industrial Safety Agency says it is unlikely that
nuclear fuel has begun melting again as the density of the xenon is low and there
has been no change in the reactor temperatures. The agency says it will continue
to monitor the xenon in the reactor.

Go to http://akiomatsumura.com/2012/04/682.html for a recent article updating the condition, number and precarious situation of the Fukashima spent fuel rods - by the former Japanese ambassador to Switzerland, Mitsuhei Murata.

Go to http://akiomatsumura.com/2012/04/682.html for a recent article updating the condition, number and precarious situation of the Fukashima spent fuel rods - by the former Japanese ambassador to Switzerland, Mitsuhei Murata.

"

safe - this response is in no way directed at you, only at the linked article.

I don't know where to begin. This article is a deliberately misleading assembly of conjecture, understated or incomplete fact and overstated threat. First off, the article fails to mention that the spent fuel pools are intact. They always were intact and they never lost water. What they lost was the ability to recirculate water. That is no longer an issue.

All 6 of the FD plants are already shutdown. So if Unit 4 collapses, it will not cause a shutdown of all 6 plants.....because they already are.

Let's examine DADE Alvarez' "astounding response"....

"304 fresh and unirradiated fuel cells." Big deal. New fuel can be and is routinely stored in air. The cells haven't been exposed to a moderator, they don't contain fission by-products on an significant scale. There is no decay heat generation. The radiation levels on contact with the fuel matrix will read background. I personally inspected every single new fuel cell that went into my submarine during a refueling overhaul - I got more exposure from the cement walls of the drydock than I did from the new fuel.

982 million Curies of of intermediate and long-lived radionuclides contained within the matrices of the remaining spent fuel cells. Of which, 393 million Curies are Cs-137. Sounds like a pretty good estimate. 200 times that which was released at Chernobyl? How about a little journalistic integrity here folks? The stark difference is that Chernobyl RELEASED that amount of Cs-137. The estimated 393 million Curies in the fuel cells at Fukushima Daichii are locked and contained within the zirc matrix of the spent fuel cells. Locked within fuel cells that are structurally intact, covered with water and with accompanying very low decay heat generation one year out after the accident - and dropping.

"Many of our readers might find it difficult to appreciate the actual meaning of the figure, yet we can grasp what 200 times more Cesium-137 than the Chernobyl would mean. It would destroy the world environment and our civilization. This is not rocket science, nor does it connect to the pugilistic debate over nuclear power plants. This is an issue of human survival."

For those of you allergic to hyperbole, you better hit your thigh with an Epi Pen now.......

Why does the article not discuss the real likelihood and mechanism by which all of this Cs-137 would be released from the fuel cells? Collapse of the building at Unit 4 would be bad, but the idea that thousands of spent fuel cells would now be scattered about the complex and just now "leaking" millions of Curies of Cs-137 is an overstated threat. Okay fine, I'll call it what it is - preposterous. Somebody please come up with a credible scenario by which this entrained Cs-137 would be released from the spent fuel. Hint: A collapsed building isn't it.

The comparative metrics this article uses are poison pill arguments. There is no utility in comparing the amount of Cs-137 released at Chernobyl or released during atmospheric weapons testing and reprocessing to an amount of Cs-137 that is trapped in undamaged, structurally intact, relatively stable spent fuel cells with low - and lowering - decay heat generation levels.

But headlining an article with such metrics does generate hits on a website...........

Could you address the concern that if cooling of the SFP fails this could result in spent fuel rods catching on fire> melts cladding>release of radio nuclides>carbon--based workers forced to evacuate>no further remediation work possible at entire Fuku 1 plant?

I probably have some of that wrong but it seems to be the doomsday scenario being bandied about now.

Also, I would be curious to know what you make of the recent revelation by Tepco that a 35 ton crane had fallen into the SPF of unit three but Tepco has "not found any indication it damaged the pool's walls and caused any leaks, or that it damaged the spent fuel". http://www.japantimes.co.jp/text/nn20120415a4.html To this layman Tepco's findings seem implausible.

Could you address the concern that if cooling of the SFP fails this could result in spent fuel rods catching on fire> melts cladding>release of radio nuclides>carbon--based workers forced to evacuate>no further remediation work possible at entire Fuku 1 plant?

I probably have some of that wrong but it seems to be the doomsday scenario being bandied about now.

Also, I would be curious to know what you make of the recent revelation by Tepco that a 35 ton crane had fallen into the SPF of unit three but Tepco has "not found any indication it damaged the pool's walls and caused any leaks, or that it damaged the spent fuel". http://www.japantimes.co.jp/text/nn20120415a4.html To this layman Tepco's findings seem implausible.

According to what I understand from even Gundersen, things won't start blowing up like they did a year ago: There just isn't enough energy left for that. What could happen though is that trying to keep it cool (if not just to make sure the shielding does not melt), vapor forms and contamination starts escaping again, or worse if a big earthquake hits Fukushima again, the spent fuel might get thrown onto the ground and then all hell would break loose, but again, no explosions or anything like that. Just something that would eat at Japan, relentlessly over the next few centuries...

Could you address the concern that if cooling of the SFP fails this could result in spent fuel rods catching on fire> melts cladding>release of radio nuclides>carbon--based workers forced to evacuate>no further remediation work possible at entire Fuku 1 plant?

I probably have some of that wrong but it seems to be the doomsday scenario being bandied about now.

Also, I would be curious to know what you make of the recent revelation by Tepco that a 35 ton crane had fallen into the SPF of unit three but Tepco has "not found any indication it damaged the pool's walls and caused any leaks, or that it damaged the spent fuel". http://www.japantimes.co.jp/text/nn20120415a4.html To this layman Tepco's findings seem implausible.

debu -

Immediately following the accident would this might have been a remote possibility due to the fuel cells most recently removed for the maintenance shutdown of Unit 4 (I think 4), but this is no longer the case. We know that for some amount of time there was no ability to add and recirculate water to the storage pools - and temperatures did indeed rise, 90C is the highest I recall reading about. Well below the point of zircalloy cladding breakdown and even further below the ignition point of zirc. We also know that the pools were and are still intact.

As far as damaging a cell? These aren't fragile things like light bulbs. They are basically flat, rolled sheets of metal. They won't just "break open" if something falls on them. After a 9.0 earthquake and follow-on tsunami, a 35 ton crane isn't much to worry about - which is precisely while you will read about it because the press has no idea what to make of real information so they will sensationalize everything. Hence the doomsday scenario being kicked around.

While it's not a zero chance event (like the Cubs winning the World Series in my lifetime), the total meltdown, ignition, degradation and release of fission products from the spent fuel scenario is pretty remote. Even the fuel matrices inside the once recently operating reactor vessels have cooled and stabilized (somewhat). Those reactors are still the primary threat and issue facing the Japanese response teams going forward with stabilization and clean-up efforts.

Could you address the concern that if cooling of the SFP fails this could result in spent fuel rods catching on fire> melts cladding>release of radio nuclides>carbon--based workers forced to evacuate>no further remediation work possible at entire Fuku 1 plant?

I probably have some of that wrong but it seems to be the doomsday scenario being bandied about now.

Also, I would be curious to know what you make of the recent revelation by Tepco that a 35 ton crane had fallen into the SPF of unit three but Tepco has "not found any indication it damaged the pool's walls and caused any leaks, or that it damaged the spent fuel". http://www.japantimes.co.jp/text/nn20120415a4.html To this layman Tepco's findings seem implausible.

According to what I understand from even Gundersen, things won't start blowing up like they did a year ago: There just isn't enough energy left for that. What could happen though is that trying to keep it cool (if not just to make sure the shielding does not melt), vapor forms and contamination starts escaping again, or worse if a big earthquake hits Fukushima again, the spent fuel might get thrown onto the ground and then all hell would break loose, but again, no explosions or anything like that. Just something that would eat at Japan, relentlessly over the next few centuries...

Samuel

Samuel -

Of course Gunderson has to change his tune. The rest of the band was in the key of G and he was singing in the key of D flat.

I think you are confused with the scenario you propose....there is very little decay heat left in the spent fuel cells. It's not negligible, but it's very manageable. Even with a loss of recirculation ability like we had in the initial days following the accident the zircalloy cladding (I think that is what you really mean by "shielding") on the fuel cells didn't melt or burn. Without a serious breach of structural integrity of the fuel cells, there is no way for entrapped fission products and fission product poisons to escape the fuel matrix and enter the environment.

The scenario the press seems to be very fond of lately is the earthquake that will "toss fuel cells about the grounds" Any earthquake that large is going to be much more of a concern than what gets tossed. And as I have addressed in earlier posts, the fuel cells are spent - there is no plausible way for an earthquake to spill these fuel cells out where they arrange themselves in any kind of geometry where they will start fissioning again. Let's not forget that they are SPENT FUEL CELLS. They might be laying on the ground, but they are not surrounded by a neutron moderator so they won't fission. At all. They won't melt either. They will simply be picked up and removed in the world's largest game of nuclear pick up sticks. Not a trivial tasking, but certainly not the Doomsday event still being chattered about today.

I think you are confused with the scenario you propose....there is very little decay heat left in the spent fuel cells. It's not negligible, but it's very manageable. Even with a loss of recirculation ability like we had in the initial days following the accident the zircalloy cladding (I think that is what you really mean by "shielding") on the fuel cells didn't melt or burn. Without a serious breach of structural integrity of the fuel cells, there is no way for entrapped fission products and fission product poisons to escape the fuel matrix and enter the environment.

The scenario the press seems to be very fond of lately is the earthquake that will "toss fuel cells about the grounds" Any earthquake that large is going to be much more of a concern than what gets tossed. And as I have addressed in earlier posts, the fuel cells are spent - there is no plausible way for an earthquake to spill these fuel cells out where they arrange themselves in any kind of geometry where they will start fissioning again. Let's not forget that they are SPENT FUEL CELLS. They might be laying on the ground, but they are not surrounded by a neutron moderator so they won't fission. At all. They won't melt either. They will simply be picked up and removed in the world's largest game of nuclear pick up sticks. Not a trivial tasking, but certainly not the Doomsday event still being chattered about today.

Yes, thanks for correcting me: the cladding.

Look, they picked up 73 Sv/h when moving a bot around inside Unit 2. Do you seriously expect anyone to believe that if the whole batch of "spent fuel" gets yanked to the ground that it will not emit at 73 Sv/h anywhere over the pile of fuel cells? I would seriously like to understand what I am missing here because I don't see how anyone would ever be able to get close to that pile...

I think you are confused with the scenario you propose....there is very little decay heat left in the spent fuel cells. It's not negligible, but it's very manageable. Even with a loss of recirculation ability like we had in the initial days following the accident the zircalloy cladding (I think that is what you really mean by "shielding") on the fuel cells didn't melt or burn. Without a serious breach of structural integrity of the fuel cells, there is no way for entrapped fission products and fission product poisons to escape the fuel matrix and enter the environment.

The scenario the press seems to be very fond of lately is the earthquake that will "toss fuel cells about the grounds" Any earthquake that large is going to be much more of a concern than what gets tossed. And as I have addressed in earlier posts, the fuel cells are spent - there is no plausible way for an earthquake to spill these fuel cells out where they arrange themselves in any kind of geometry where they will start fissioning again. Let's not forget that they are SPENT FUEL CELLS. They might be laying on the ground, but they are not surrounded by a neutron moderator so they won't fission. At all. They won't melt either. They will simply be picked up and removed in the world's largest game of nuclear pick up sticks. Not a trivial tasking, but certainly not the Doomsday event still being chattered about today.

Yes, thanks for correcting me: the cladding.

Look, they picked up 73 Sv/h when moving a bot around inside Unit 2. Do you seriously expect anyone to believe that if the whole batch of "spent fuel" gets yanked to the ground that it will not emit at 73 Sv/h anywhere over the pile of fuel cells? I would seriously like to understand what I am missing here because I don't see how anyone would ever be able to get close to that pile...

Samuel

Samuel -

Now you have changed the scenario. While the spent fuel cells can no longer be used in an operating core to generate heat to run the steam turbines - hence the term "spent fuel", they are still very highly radioactive, and that would be the issue to deal with if the cells were to somehow get 'tossed' all over the place. They would be point source emitters (possibly plane source emitters depending on the dimensions of the pile) - for a point source emitter, the radiation exposure falls off at a 1/r squared function. It would be nearly impossible for humans to work right up against the fuel cells for any amount of time, but the cells could be picked up by robotics or long boom cranes and placed in shielded containers. It would (still) be a localized event and situation. Not an ideal situation by any means, but this whole discussion about earthquakes tossing them to the ground with burning and melting and fissioning is utter nonsense.

Now you have changed the scenario. While the spent fuel cells can no longer be used in an operating core to generate heat to run the steam turbines - hence the term "spent fuel", they are still very highly radioactive, and that would be the issue to deal with if the cells were to somehow get 'tossed' all over the place. They would be point source emitters (possibly plane source emitters depending on the dimensions of the pile) - for a point source emitter, the radiation exposure falls off at a 1/r squared function. It would be nearly impossible for humans to work right up against the fuel cells for any amount of time, but the cells could be picked up by robotics or long boom cranes and placed in shielded containers. It would (still) be a localized event and situation. Not an ideal situation by any means, but this whole discussion about earthquakes tossing them to the ground with burning and melting and fissioning is utter nonsense.

Yes, I am talking about that: spent fuel getting tossed over the ground and not being able to do anything about.

I guess we can choose to believe that we are smart enough to come up with the kind of technology needed to pick up that mess, but it doesn't prove that we actually can.

So, what if we can't? Can this cladding resist rain, erosion and radioactivity for 10000 years? What if a couple of those claddings crack? Stuff comes out right? And where is it going to end up?

That's what I'm talking about. Nobody's talking about what we could do if that happens. We are just praying very hard that it does not happen over the course of the next 30 years, the minimum amount of time they expect to wrap up Fukushima, in the relative good state that it is now...

Now you have changed the scenario. While the spent fuel cells can no longer be used in an operating core to generate heat to run the steam turbines - hence the term "spent fuel", they are still very highly radioactive, and that would be the issue to deal with if the cells were to somehow get 'tossed' all over the place. They would be point source emitters (possibly plane source emitters depending on the dimensions of the pile) - for a point source emitter, the radiation exposure falls off at a 1/r squared function. It would be nearly impossible for humans to work right up against the fuel cells for any amount of time, but the cells could be picked up by robotics or long boom cranes and placed in shielded containers. It would (still) be a localized event and situation. Not an ideal situation by any means, but this whole discussion about earthquakes tossing them to the ground with burning and melting and fissioning is utter nonsense.

Yes, I am talking about that: spent fuel getting tossed over the ground and not being able to do anything about.

I guess we can choose to believe that we are smart enough to come up with the kind of technology needed to pick up that mess, but it doesn't prove that we actually can.

So, what if we can't? Can this cladding resist rain, erosion and radioactivity for 10000 years? What if a couple of those claddings crack? Stuff comes out right? And where is it going to end up?

That's what I'm talking about. Nobody's talking about what we could do if that happens. We are just praying very hard that it does not happen over the course of the next 30 years, the minimum amount of time they expect to wrap up Fukushima, in the relative good state that it is now...

Samuel

Samuel -

I understand your concerns, but rest assured there is plenty we can do about them The technology already exists to safely handle spent fuel cells. The short answer is we can pick up that mess.

Zirc cladding is very, very resistant to corrosion and the elements. Remember, it was manufactured to operate under extreme temperatures and pressures, and in a neutron flux. I think you mean corrosion instead of erosion, and yes, a fuel cell is more than capable of standing up to the elements. Remember, the fuel cells aren't like eggs or light bulbs, nothing will "leak" out if there are surface cracks. There is a good reason why zirconium cladding is used - zirc 4 alloy is used for the outer layer because it is very resistant to pitting, corrosion and steam crevice corrosion. It develops an extrememly thin (nanometers thick) passivation layer of zirc oxide that all but shuts off further oxidation and corrosion. Zirc 2 alloy is rolled inside the zirc 4 cladding - it does a great job of holding the fuel particles together and is also corrosion resistant. Both zirc 4 and zirc 2 have a very low neutron absorption cross sections so they are ideal for use in nuclear fuel cells. Zirc 2 and zirc 4 are subject to hydrogen embrittlement if subjected to steam for prolonged periods of time. It will absorb hydrogen if present and may with time cause blistering and cracking of the zirc 4. This could lead to release of fission product daughters. But since the spent fuel cells weren't subject to steam, the chances of them having residual hydrogen blisters or bubbles from previous normal operations is slim. So even if they were on the ground, they would remain intact and corrosion resistant for quite some time.

Trust me, people are talking about what to do if the building collapses and you can be confident that contingency plans for such an event are at least being discussed if not already in place. If it did happen, it will be an issue to deal with, but it certainly won't be the "Mass Extinction" event that has been flying around cyber space the past couple of days.

Keep the questions coming - I want to make sure you and others are as well informed as possible within the scope of my knowledge and experience. If I know the answer, I'll tell you. If I don't know the answer, I'll find it out for you. If I am maing an educated guess, I'll let you know that as well.

I understand your concerns, but rest assured there is plenty we can do about them The technology already exists to safely handle spent fuel cells. The short answer is we can pick up that mess.

Zirc cladding is very, very resistant to corrosion and the elements. Remember, it was manufactured to operate under extreme temperatures and pressures, and in a neutron flux. I think you mean corrosion instead of erosion, and yes, a fuel cell is more than capable of standing up to the elements. Remember, the fuel cells aren't like eggs or light bulbs, nothing will "leak" out if there are surface cracks. There is a good reason why zirconium cladding is used - zirc 4 alloy is used for the outer layer because it is very resistant to pitting, corrosion and steam crevice corrosion. It develops an extrememly thin (nanometers thick) passivation layer of zirc oxide that all but shuts off further oxidation and corrosion. Zirc 2 alloy is rolled inside the zirc 4 cladding - it does a great job of holding the fuel particles together and is also corrosion resistant. Both zirc 4 and zirc 2 have a very low neutron absorption cross sections so they are ideal for use in nuclear fuel cells. Zirc 2 and zirc 4 are subject to hydrogen embrittlement if subjected to steam for prolonged periods of time. It will absorb hydrogen if present and may with time cause blistering and cracking of the zirc 4. This could lead to release of fission product daughters. But since the spent fuel cells weren't subject to steam, the chances of them having residual hydrogen blisters or bubbles from previous normal operations is slim. So even if they were on the ground, they would remain intact and corrosion resistant for quite some time.

Trust me, people are talking about what to do if the building collapses and you can be confident that contingency plans for such an event are at least being discussed if not already in place. If it did happen, it will be an issue to deal with, but it certainly won't be the "Mass Extinction" event that has been flying around cyber space the past couple of days.

Keep the questions coming - I want to make sure you and others are as well informed as possible within the scope of my knowledge and experience. If I know the answer, I'll tell you. If I don't know the answer, I'll find it out for you. If I am maing an educated guess, I'll let you know that as well.

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Thanks for the technical info! Technically I suppose there are good chances of getting out of that mess, but only if we're actually serious about it. Although I'm not convinced we have the technology, I think we could probably come up with hacks if we're motivated enough (as was the case with the Macondo blowout, for example).

My main concern are the Japanese government/TEPCO and the international community. IMO, they're not motivated.

[quote] But the word from the national government was totally unexpected. "It's impossible for a nuclear power plant to have an accident. [...] Dr. Haruki "Detarame" (falsehood) Madarame told then-Prime Minister Naoto Kan on board the helicopter on the way to Fukushima I Nuke Plant on March 12, 2011, "Don't worry. It's impossible for the reactor to blow up. It's structurally impossible." [/quote]

So, forgive my paranoia, but I seriously doubt anyone with any sort of authority in Japan is thinking about what to do if the spent fuel pool finds its way to the ground. (They're too busy debating tax increases and quantitative easing.) I also seriously doubt that TEPCO has any intention of following up on their plans to build an underground wall to stop polluted underground water from contaminating the rest of Honshu (the main Japanese island).

Suffice to say, I won't be buying land or real estate anywhere on Honshu.